The present invention relates to a steam producing apparatus for home use, fed by a cold water reservoir.
Presently these apparatuses are used in steam household appliances, such as steam irons or apparatus to clean carpets, moquette and the like.
It is known that these steam producing apparatus are equipped with a boiler provided with a resistor designed to heat and vaporize water. This boiler has a steam outlet duct and a water admitting element which can be a filler or a duct connected to a reservoir.
The use of boilers directly admitting water through the filler on the part of a user, is somewhat dangerous when the water topping up is to be carried out, and also has other drawbacks.
In fact, in order to eliminate the risk of dangerous steam jets when cold water is added into the boiler, a separate cold water reservoir connected to the boiler by a pump has been used.
This arrangement has been depicted in the Italian patent application for utility model No. 21475B/83.
The described apparatus comprises a boiler provided with an electric resistance heating element to heat and vaporize water, a water cold reservoir independent of the boiler and a pump in fluid communication with the boiler on one hand, and the reservoir on the other hand. The pump enabling the water to enter the boiler from the reservoir is activated by a detector detecting the minimum water level in the boiler and deactivated by another maximum water level detector.
It has been found that the use of a cold water reservoir connected to the boiler through a duct eliminates some problems but leaves other problems unsolved.
In fact, while the apparatus of the above described type have proved to have a good efficiency in operation, some drawbacks have however been found due to the prolonged use of the apparatus.
One problem resides in the fact that the topping-ups in the reservoir are effected on the discretion of the user who must periodically check the water level. As a result, so long as there is water in the reservoir the pump carries out the subsequent boiler fillings upon command of minimum and maximum water level detectors and the apparatus works properly.
However, as soon as the reservoir is empty, the steam delivery is no longer homogeneous because the water used is that remaining in the boiler until it is completely exhausted.
Then another problem originates from the fact that when the water in the reservoir and the boiler has been depleted, the heating element becomes overheated since it is no longer cooled by the water. This fact brings about an alteration in the good operation of the apparatus unless the use of thermostats is provided which on the other hand cannot ensure an immediate intervention.
A further problem arises each time water is admitted to the boiler from the reservoir. In fact if given equilibrium conditions are not maintained between the water and steam amounts and consequently between temperature and pressure, under this condition it will be necessary to wait before having steam delivered again, due to the fact that the temperature of the water in the reservoir is lower than that in the boiler.